Detecting welds



Aug. 8, 1961 L. A. FUGASSI, JR

DETECTING WELDS Filed June 9, 1958 2 Sheets-Sheet 1 l 3) SHIELDED 7) 9)ll) END ARC PLAT/N6 SHEET PIN HOLE 'sH,4R BUTT Luv/5s SHEAR DETECTORWELDER 5 INVENTOR.

LUC/EN A. FUGASSI, JR

BY wwmm 4 TTORNEV Aug. 8, 1961 A. FUGASSI, JR

DETECTING WELDS 2 Sheets-Sheet 2 Filed June 9, 1958 SOURCE WELD/N6CURRENT WELDING CURRENT SOURCE INVENTOR. LUC/EN A. FUGA$$/, JR.

ATTORNEYS United States Patent 2,995,239 DETECTING WELDS Lucien A.Fugassi, Jr., Weirton, W. Va., assignor to National Steel Corporation, acorporation of Delaware Filed June 9, 1958, Ser. No. 740,888 6 Claims.(Cl. 209-72) The present invention relates to detecting welds, and moreparticularly to methods for producing butt-welded metallic sheet andstrip material having welded joints which are readily detectable eventhough covered by an opaque coating material.

In the formation of coated metal sheet such as tinplate, it is thecurrent practice to run the strip to be plated, such as black plate,through the electrotinplating lines in the form of a continuous strip.In order to provide a continuous strip, it is necessary to join endwisegreatly elongated strip in the form of coils. As the strip from one coilis unwound and the end of the coil reached, the free end of the stripfrom another coil is joined thereto, and so on from coil to coil, withthe result that the plating process may be conducted continuously.

In the past, it has been customary to shear the adjacent ends of thecoils to be joined and then to lap weld the adjacent ends together, asfor example disclosed in U.S. Patent No. 2,478,491, August 9, 1949. Thelap welded continuous strip emerging from the plating lines is thensheared into sheet form in another portion of the plant. Certain ofthese sheets will have a lap weld extending across them. The lap weld isrelatively hard and brittle and renders these certain sheets useless formany subsequent forming and shaping operations such as can making.Accordingly, the sheets containing the welds are separated from theremaining sheets and treated as scrap. Despite the fact that the lapwelds have been coated with an opaque tinplate, they are neverthelessvisible because they alter the normally flat contour of the sheet.Hence, the sheets containing the lap welds can be detected by visualinspection even after tinplating.

In recent years, however, it has increasingly become the practice toship tinplate from the plant in coils rather than in sheets. Theconsumer then uncoils and cuts the strip to sheet form as it is requiredin his production operations. But problems have arisen from the shipmentover long distances of lap welded strip in coil form. When the strip incoil form is transported in a truck or on a railroad car, the shimmyingof the conveyance causes the convolutions of the coil to rub and pressagainst each other. If the coil includes lap welds of a thickness twicethe thickness of the remainder of the sheet, it has been found inpractice that upon movement of the coils over long distances the weldsimpress themselves not only upon the immediately adjacent convolutionsbut also through a plurality of convolutions of the strip adjacent theweld. At the consumers plant, the coil is unwound and cut to sheet formand the lap welds visually detected and the corresponding sheetsscrapped; but there remains a substantially greater number of sheetswhich contain no weld yet are heavily marked or scored from the lapwelds.

Obviously, one solution of this problem is to butt weld the adjacentends of the coils prior to running the continuous strip through theelectrotinplating lines. The resulting coils of tinplate containing onlybutt welds can then be shipped over long distances without anyappreciable scoring of the adjacent convolutions, as the butt welds haveno appreciable difference of contour from the remainder of the strip.

Unfortunately, although the coiled tinplate may reach the consumer inperfect condition, he is presented with a problem when he cuts it tosheet form. The butt welds are essentially smooth and flush. These weldswould be visible if they were exposed, but they have been coated withtinplate and can no longer be visually detected with ease. Hence, theconsumer is confronted in effect with a stack of tinplates, all of whichlook alike but certain of which contain hidden welds which would damagehis equipment were he to use them all without first separating thosecontaining welds.

Although many attempts have been made to overcome the foregoingdifiiculties and disadvantages of this prior art, none, as far as isknown, has been entirely successful when practiced commercially on anindustrial scale.

Accordingly, it is an object of the present invention to provide methodsfor joining endwise a pair of elongated metal strips by welding in sucha way as to produce a readily detectable Weld.

Another object of the present invention is the formation betweenelongated metal strips, of readily detectable coated welds.

Still another object of the present invention is the provision ofmethods for producing coated metal sheets from butt welded strips,certain of the sheets having readily detectable welds therein.

Yet another object of the present invention is the provision of methodsfor producing from butt welded metal strip a plurality of coated sheetsall of which are free from joints.

A further object of the present invention is the provision of methodsfor forming and detecting butt Welds in the production of coated metalsheets.

Finally, it is an object of the present invention to provide methods asdescribed above which will be simple, economical and reliable in use.

Other objects and advantages of the present invention will becomeapparent from a consideration of the following description, taken inconnection with the accompanying drawing, in which:

FIGURE 1 is a diagrammatic flow sheet of the process of the presentinvention;

FIGURE 2 is a somewhat diagrammatic longitudinal cross-sectional view ofthe end shears which trim the strips prior to but welding;

FIGURE 3 is an enlarged fragmentary perspective view of one of the shearblades of the present invention;

FIGURE 4 is a fragmentary perspective view of an end of a trimmed stripprior to butt welding and showing therein one form of the deformationwhich assures the results of the present invention;

FIGURE 5 is a fragmentary perspective schematic view of the but weldingoperation in an initial stage; and

FIGURE 6 is a view similar to FIGURE 5 but showing the welding operationat a later stage.

Broadly, the present invention comprises deforming an end of a trimmedstrip to be butt welded so a to produce a protruding tang on the end ofthe strip, preferably during the shearing operation which trims thestrip, and thereafter butt welding the trimmed strip ends with anonconsumable electrode to melt them together. Where the tang protrudes,a hole will be burned through the joint between the strip ends. Afterthe continuous strip is plated or otherwise coated, the weld isinvisible but the hole through the joint is readily detachable by a pinhole detector or the like, so that after the coiled strip is cut tosheet form, the sheets bearing the joints may be separated from thosefree from joints.

Referring now to the drawings in greater detail, there is showndiagrammaticaly in FIGURE 1 a flow sheet of a process according to thepresent invention in which coils of metal strip 1 are trimmed at theirends in end shear 3 and butt welded by a welder 5 so as to produce acontinuous strip which is continuously coated in plating lines 3 7 andthen cut to sheet form in sheet shears 9. The cut sheets are thenclassified and separated in a pin hole detector 11 into a pile 13 allthe sheets of which contain welds and a pile 15 all of the sheets ofwhich are free from welds.

Specifically, strips 1 may for exampl be tin-mill black plate, which issteel strip of 29 gauge or lighter, between 12 and 45 inches in width.The coils are unrolled oneby-one for introduction into the line, the endof each coil being joined to the end of the next coil so as to produce acontinuous strip. Apart from the method of joining, the procedure ofproducing a continuous strip may be as outlined in U.S. Patent No.2,478,491, August 9, 1949. In the illustrated embodiment, the coil endsare trimmed square in end shear 3 prior to joining by butt welding. Endshear 3 comprises a pair of shearing rolls 17 and 19 power driven torotate in opposite directions and having the usual shearing blades 21and 23 which coact to shear the strip ends square in the usual manner.In this way, a flat end portion at each end of each strip is providedwith a straight end edge substantially perpendicular to the length ofthe strip. Obviously, instead of a rotary shear, a reciprocatory shearor the like could be used.

Indeed, the structure and operation of the end shear is entirelyconventional except for the fact that blade 21 is provided with a nickor notch 25 in its cutting edge, as seen in FIGURE 3. As a result, oneend of each sheared strip 1 will be formed with an upstanding burr ortang 27 corresponding to that portion of strip 1 which is disposed innotch 25 and is therefore the last to separate from the remainder ofstrip 1. There is thus formed a projection on the edge, which istransverse but not necessarily perpendicular to the plane of theassociated flat end portion.

The sheared adjacent ends of the strips are both square and are thenbutted endwise to form a smooth fiat joint. The strips are weldedtogether in shielded are butt Welder which may for example be of thetype disclosed in and operable according to the teachings of U.S. PatentNo. 2,516,016, issued July 18, 1950. A nonconsumable electrode 29 incircuit with the work is shielded by a continuous stream of an inert gassuch as helium or argon or mixtures of the two which emerges fromwelding torch 31 about the end of the electrode. Of course, types ofbutt welding other than shielded are may also be used.

During the welding operation, the are 33 between the electrode and thework is distributed over a relatively large area of the abutting edgesof the strips to be welded together and serves continuously to meltadjacent end edge portions of the strips. As the are moves on along thejoint, the melted portions leave the region of the arc and rapidly cooldown and resolidify to an integral weld 35.

However, when are 33 reaches tang 27, the distribution of the are over arelatively large area of the strip edges is destroyed and substantiallyall of the arc is concentrated through tang 27 which provides in elfecta short circuit across the gap between the electrode and the work. As aresult, there is concentrated and severe overheating of tang 27 and themetal by which it is joined to the remainder of strip 1, and this metalnot only melts but also vaporizes, a phenomenon known as burning in thewelding art. The result is that a small hole 37 remains through weld 35after the are has passed on. The hole 37 corresponds in location to tang27 and represents the loss of metal by vaporization upon burning.

The continuous strip produced by the end-to-end butt welding of strips 1passes through plating lines 7 which may be of the conventionalgalvanizing or tinplating type or of other types adapted to deposit anopaque metallic or non-metallic coating on both sides of the strip. Inthe plating lines, a metallic coating such as tin is applied to thecontinuous strip, and as is usual in the case of plating strip havingpin holes such as hole 37 therein, the plating alloy does not bridgeacross the hole but leaves a hole entirely through the strip.

There is thus produced a continuous strip having pin holes therethroughdeliberately placed at the locations of the welds. This selectivelyperforated coated strip is then fed to the sheet shear 9 and pin holedetector 11 by which it is cut into a plurality of sheets of desiredlength and width and the sheets having pin holes corresponding to holes37 therethrough directed to a defective sheet piler 13 while theremaining sheets pass to the prime sheet piler 15. As is usual,detection of the pinholes is accomplished by the completion of aphotoelectric circuit through the pin holes. Of course, it is immaterialWhether the pin holes are detected before or after the strip is shearedto sheet form, and a suitable mechanism for detecting pin holes,shearing the strip to sheet form and assorting the sheets according tothe presence or absence of pin holes therein is disclosed in DowellPatent No. 2,433,685, December 30, 1947, the disclosure of which isincorporated by reference in the present application toavoid theneedless repetition of the subject matter thereof. Needless to say,sheets having pin holes other than those deliberately created at thelocation of the butt welds will be directed to defective sheet piler 13,so that the sheets in piler 13 will not necessarily all have weldstherein. On the other hand, none of the sheets in piler 15 will havewelds there in, and these latter sheets may then be used in fabricatingequipment such as can making machinery without damage to the machinery.It is also within the scope of this invention that the pin hole detectormerely mark the sheets or portions of the uncut strip having perforatewelds therein, so that the prime and defective sheets may later besorted by visual inspection. Such automatic marking followed by sortingby visual inspection, as well as the other methods of sorting recitedabove, comprise separating the sheets containing the joints from the remaining sheets by means automatically responsive to the presence of theholes.

From a consideration of the foregoing, it will be obvious that all ofthe initially recited objects of the present invention have beenachieved.

Although the present invention has been described and illustrated inconnection with preferred embodiments, it is to be understood thatmodifications and variations may be resorted to without departing fromthe spirit of this invention, as those skilled in this art will readilyunderstand. For example, it is also within the contemplation of theinvention in its broader aspects to form the holes at the welds bymethods other than that specifically recited above. Such modificationsand variations are considered to be within the purview and scope of thepresent invention as defined by the appended claims.

What is claimed is:

l. A method of joining endwise a pair of elongated metal strips eachhaving a fiat end portion terminating in a straight end edge, comprisingthe steps of forming a projection on at least one of said straight endedges intermediate the ends thereof and transverse to the plane of theassociated flat end portion, butting said edges, and progressivelymelting said butted edges with a nonconsumable electrode to form abutt-welded joint having a hole therethrough at the location of theprojection.

2. A method of producing a coated metal strip from a pair of elongatedmetal strips each having a fiat end portion terminating in a straightend edge, comprising the steps of forming a projection on at least oneof srid straight end edges intermediate the ends thereof and transverseto the plane of the associated flat cnd portion, butting said edges,progressively melting said butted edges with a nonconsumable electrodeto form a outtwelded joint having a hole therethrough at the location ofthe projection, and coating both sides of the joined strips with anopaque coating of a desired thickness without closing the hole.

3. A method of producing a plurality of metal sheets from a pair ofelongated metal strips each having a straight end edge, comprising thesteps of butt-welding said end edges together with a hole through thebutt-welded joint intermediate the ends of the joint, cutting the joinedstrips transversely of their length into a plurality of sheets one ofwhich contains the joint, and separating the sheet containing the jointfrom the remaining sheets by means automatically responsive to thepresence of the hole thereby to obtain a plurality of sheets all ofwhich are free from joints.

4. A method of producing a plurality of coated metal sheets from a pairof elongated metal strips each having a straight end edge, comprisingthe steps of butt-welding said end edges together with a hole throughthe butt- Welded joint intermediate the ends of the joint, coating bothsides of the joined strips with an opaque coating of a desired thicknessWithout closing the hole, cutting the joined strips transversely oftheir length into a plurality of sheets one of which contains the joint,and separating the sheet containing the joint from the remaining sheetsby means automatically responsive to the presence of the hole thereby toobtain a plurality of coated sheets all of which are free from joints.

5. A method of producing a plurality of metal sheets from a pair ofelongated metal strips each having a flat end portion terminating in astraight end edge, comprising the steps of forming a projection on atleast one of from the remaining sheets by means automatically responsiveto the presence of the hole thereby to obtain a plurality of sheets allof which are free from joints.

6. A method of producing a plurality of coated metal sheets from a pairof elongated metal strips each having a flat end portion terminating ina straight end edge comprising the steps of forming a projection on atleast one of said straight end edges intermediate the ends thereof andtransverse to the plane of the associated flat end portion, butting saidedges, progressively melting said butted edges with a nonconsumableelectrode to form a butt-Welded joint having a hole therethrough at thelocation of the projection, coating both sides of the joined strips withan opaque coating of a desired thickness without closing the hole,cutting the joined strips transversely of their length into a pluralityof sheets one of which contains the joint, and separating the sheetcontaining the joint from the remaining sheets by means automaticallyresponsive to the presence of the hole thereby to obtain a plurality ofcoated sheets all of which are free from joints.

References Cited in the file of this patent UNITED STATES PATENTS saidstraight end edges intermediate the ends thereof and 25 1 426 6,83Stalhane 22 1922 transverse to the plane of the associated flat endportion, 1512787 Morton i jj 1924 butting said edges, progressivelymelting said butted edges 1 1 34 with a nonconsumable electrode to forma butt-Welded 047:221 pechy f July 14: 1936 joint having a holetherethrough at the location of the 2 433, 35 D ll D 30, 1947projection, outing the joined strips transversely of their 30 2,516,016P kala July 18, 1950 length into a plurarity of sheets one of whichcontains 2,649,528 Koenig et a1. Aug. 18, 1953 the joint, and separatingthe sheet containing the joint UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 2,995,239

August 8, 1961 Y Lucien A. Fugassi Jr.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent. should read as"corrected below.

Column 2, lines 43 and 51, for "but", each occurrence, read butt line63, for "detachable" read detectable column 5, line 31, for-Y'plurarity" read plurality I (SEAL),

Attest:

DAVID L. LADD Commissioner of Patents ERNEST w. .SWIDER AttestingOfficer USCOMM-DC- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 2,995,239 August 8, 1961 Lucien A. Fugassi, Jr.

Column 2, lines 43 and 51, for "but" read butt line 63, for "d each occurrence, column 5, line 31,

etachable" read detectable for "plurarity" read plurality Signed andsealed this 2nd day of January 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD Attesting Officer I Commissioner ofPatents USCOMM-DC UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 2,995,239 August 8, 1961 Lucien A. Fugassi, Jr.

Column 2, lines 43 and 51, for "but" read butt line 63, for "d each occurrence, column 5, line 31,

etachable" read detectable for "plurarity" read plurality Signed andsealed this 2nd day of January 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD Attesting Officer I Commissioner ofPatents USCOMM-DC UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 2,995,239 August 8, 1961 Lucien A. Fugassi; Jr.

It is hereby certified that error appears in the above numbered pat entrequiring correction and that the said Letters Patent. should read as"corrected below.

Column 2, lines 43 and 51, for "but" read butt'-; line 63, for '.'dcolumn 5, line 31, for

each occurrence, etachable" read detectable 7"plurarity" read pluralitySigned and sealed this 2nd day of January 1962.

(SEAL) Attest:

ERNEST W. SWIDER" DAVID L. LADD Attesting Officer Commissioner ofPatents USCOMM-DC

